Burglar alarm



May 14, 1929. F. L. KOHLER 1,712,771

BURGLAR ALLY! Filed Aug. 27, 1927 VBEI ii'vedenick L eslie Jfohler;

lhatenteel May id,

ALA

Application filed August 2?, 1927.

The invention is designed to furnish a burglar alarm for windows, doorways or other openings through which ingress may be attempted to be made to a building by an unauthorized person. One object is to provide means whereby the entire opening will be protected against access of a burglar, so that no matter at what part of the window or door the 'burglar'may direct his work of breaking in, an alarm will be set 03 as a result of the closing'of a circuit controlled by the protector.

The invention consists in the features and combination and arrangement of parts hereinafter described and particularly pointed out in the claims.

Tn the accompanying drawings:

ll ig. l is a View of so much of the appliance as is necessary to illustrate its assembly witn the signal, the battery and the circuit con nections. Y

Fig. .2 is a view of the protector employed for closing the window or door openingagainst the entrance of an unauthorized person, the view being a side elevation of the inner side of the appliance.

Fig. 3 is a view similar to Fig. 2 of a portion of the protector on a larger scale in respect to l. i

Fig. l is a vertical sectional view on an enlarged scale of a portion of the protector.

rig. 5 IS a horizontal sectional view or a: part of the protector showing a hinge connection by which it may be mounted in a doorway or window opening.

Tn these drawings 1 indicates a frame com posed of electric Insulating material such as fibre, wood, or any other suitable material covered with insulating substance. This frame is composed of top, bottom and side rails 2, 3 and 4. Wire screen material covers the opening through this frame. This wire screen is in two sheets or layers. One of these, 5, is on the inner side of the frame, and the other, 6, is on the outer side of the frame, and as the rails of the frame are about one quarter of an inch thick, the two sheets of wire screen material will be spaced apart about one quarter of an inch. This screen material is made of wire capable of conducting'electric current, as for instance copper. The two spaced apart sheets or layers are secured to the frame by brass strips 7 and 8, t e former being on the inner side and the DISTRICT 03 COLUMBIA.

latter on the outer side of the frame. These strips clamp the sheets of wire screen material between themselves and the insulating frame composed of the bars 2, 3 and 4.

The clamping strips are secured in place by two sets of fastening devices, which differ in form relative to each other because of the difi'erent conditions to be met, owing to the fact that one strip is on the outer side of the protector and the other is on the inner side of the said protector. The means for fastening the outer strip 8 in place consists of the cap screws 9 having their heads 10 seated in recesses 11. on. the inner side of the frame and with their stems screw threaded at 9' and seated in screw threaded openings in the strip 8. by which the strip can be drawn into firm clamping contact with the wire screen material for holding it at its margin to the frame. The screw threads on these cap screws do not engage the material of the frame, hence the screw, if an attempt is. made to bore away its outer end, will be free to slide longitudinally and make contact with the inner screen materialand further as the end of the screw contacts with the outer screen or the tool which is being used in the boring operation and because the latter will touch the outer screw, electrical connection will exist between the outer and inner screws and hence the burglar alarm will sound, it being understood,-as hereinafter described, that the two screws form the terminals of an electric circuit which includes within it the alarm.

For holding the screen 5 on the inner side of the closure or protector the brass strip 7 is secured to the frame by bolts 12 in the form of stove bolts, each having a conical head with a lrerf for a screw driver, a threaded stem and a 13. The latter is seated in a recess 14- on the outer side of the frame, but within the outer screen member. The heads 15 of these bolts are exposed on the inner side of the protector, but as theside faces the inside of the building these heads are not accessible to a burglar endeavoring to gain entrance into the building.

A? 16 I show clips attached to the frame by the bolts 12 and adapted to secure the protector to the winuov: or door frame for which purpose said clips have openings as at 17 to receive screws to attach the device to the window or door frame. These SCI'GW 3S S0011 being on the inner side'of the protector, are

inaccessible from the outside of the building. Instead of clips a hinge member may be employed as shown at 16 so that the protector can be swung out of the way when not in use. With this construction. may be used any suitable form of fastening on the inner side of the protector.

' As before stated, these spaced apart screen members are the contacts of an electrical circuit and the intention is that if they are brought into contact at any point they will close the circuit and the alarxnwill sound. They coverthe entire opening. The space between them is small so that if pressed upon I at any point of their free surfaces they will come together and close the circuit. If attempt to cut them out is made, it will be impossible to do this without closing the circuit either by the screens contacting with each other or the cutting implement forming the electrical connection between them. These sheets of material forming the circuit closing means being made of wire screen material, will not interfere with visibility, so that a patrolman can view the interior of the building through the protector, nor will the protector obstruct the passage of light from outside to inside and the same is true of air, which can have free circulation to and from the room protected by the device.

As before stated, on the outer side no fastening means are employed which can be removed. The only thing appearing on the outer side is the ends of the cap screws. These can not be removed from the outer side of the protector and if'attempt is made to drill them out, not only will this require much time but the circuit would be closed by the movement of remaining part of the as it is freed from its seat in the brass strip.

Furthermore the openings in the outer brass strip need not be employed, but instead the outer ends of the screws may be seated in sockets passing only part way through the outer brass strip so that the outer face of this strip is intact from end to end, coverl'ng completely the fastening devices against access from the outer side of the unit.

The sockets 14 are of such shape as will hold the nuts 13 against turning while stove bolts 12 are being screwed into place.

In assembling the protector the outer wire screen is placed in position with the outer brass strip thereon and the screws 9 are then screwed into place. The inner screen 5 is then placed in position with its brass strip after having first placed the nuts in'position and then the stove bolts are turned into place, engaging the nuts.

Any suitable circuit connections may be employed and this is true also of the alarm. In Fig. 1 I show one form of connection including a battery a with a primary circuit 12,

0, d including a relay,

The armature f of this relay is in the form of a catch holding up a circuit closing arm 9 so that when the relay is energized this arm g will fall and close a secondary circuit at h, which includes the wire 5, battery a, part of wire b, the signal SIG. and wire j, which circuit will remain closed, keeping the. signal in operation until said circuit is manually opened by a reset button. This reset button is shown at k. The two sheets of spaced apart wire screens are electrically connected respectively with the wires 6 and d so that if these screens come in contact at any point the circuit will be closed and the alarm sounded. i

It will be seen from the above that the circuit will be closed when the screens are relatively deformed oraltered from their normal relation, whether by pressing one upon the other, rupture, or cutting.

Theprotector may be used in situations leaf 16*.of said hinge to lie between the said hinge member and the wall or frame to which the hinge is attached.

The protector may at the lock of the window sashes or door, it preferably, being placed on the inner side of said window or door. I

The brass strip 7 at the sides of the frame cross the joints between the side and top and bottom rails of the main frame and these serve to brace thesame to provide a frame of a self sustaining character. In other words these brass strips reinforce the frame so that it may be used in various situations and under various conditions without getting out of shape. dow opening or it can be removably mounted to be readily removed and set aside as in the case of protecting a doorway or it can be mounted on a hinge. In either case it will withstand handling without losing its she. or sag 'ng and because of its bracin by t a metallic" strips the main frame can be made of comparatively thin material thus enabling lightness to be attained without sacrificing strength.

Further the structure insures efficiency in operation because with a frame which will maintain its original shape there will be no danger of the wire screens sagging and possibly coming in contact and setting oi! the alarm when there is no existing danger condition.

The strips 7 being formed of brass will serve as electric conductors.

I claim: 1

1. A circuit closer for a burglar alarm comprising a frame, wire screens carried thereby be swung aside to get It can be used as a fixture in the wm- 1 in spaced apart relation, and two sets of means fol-holding the screens to the frame,'both sets of said means being accessible for removal only from the inner side of said frame, substantially as described.

' 2. Apparatus according to claim 1 in which the outer screen is held in place by screws contacting ,therewith and having their heads countersunk in the inner face of the frame and spaced apartfrom but adjacent the inner screen, and the inner screen is'held in place by bolts contacting therewith and having their nuts countersunk in the outer face of the frame andspaced apart fromlthe outer screen.

3. In combination a-frame, inner and outer sheets of screen material carried by said frame in spaced apart relation, strips of electrically conductive material overlying and in contact with the screen material and means for fastening said strips in place, said fastening means extending, through the frame and the frame has a hinge mounting, one member of said hinge lying between the screen material and its'overlying metallic strip on one side and the frame member onthe other side, substantially as described.

6.- In combination a frame, an inner and an outer screen, devices for holding said screens in place consisting of screw accessiblefor manipulation only upon the inner side of said frame, a hinge having one member electrically connected with one of the screens and held in place by one of the screws, said hinge serving as part of the electric alarm circuit of which the screens form the terminal.

In testimony whereof I a-fiix my signature."

FREDERICK LESLIE K'oHLER, 

